1. Field of the Invention
The present invention relates to an image processing apparatus, and, more particularly, to an image processing apparatus capable of, for example, binary encoding entered data of an original image in which the binary image regions, such as characters, and half-tone image regions, such as photograph, are mixed.
2. Description of the Related Art
Hitherto, in the apparatus of the type described above, there has been a binary encoding apparatus capable of processing binary image information expressing, for example, documents, characters, and drawings and as well capable of processing multi-valued image information expressing half-tone image (one of the multi-valued information) information such as photograph or the like.
For example, in an apparatus capable of binary encoding multi-valued information, the binary image regions of the binary image information and the half-tone image regions of the half-tone image information are read from the original image by the image reader. Next, the image information transmitted from this image reader is processed by the following binary encoder. In this binary encoding portion, a image processing in accordance with the density of the entered image information is performed. In this case, the image information transmitted from the image reader has been subjected to a correction treatment in accordance with a information representing the characteristics of the output information, such as the density of the pixels or the contrast, and is expressed by the density level corresponding to the density of the pixels as data. The thus-transmitted image information from the image reader is then subjected to an identification treatment for distinguishing whether it is a character region or a photograph region. In this identification treatment, the differences between the density level of the subject and those of the pixels around the subject pixel are obtained. The identification for determining whether the subject region is a character region or a photograph region is performed by making comparison between the difference which shows the maximum level selected from the differences obtained as described above and a predetermined threshold.
However, in a case where the image reader transmits image information with the density level, the region which is in fact a photograph region can be mis-identified as a character region if a predetermined density difference is detected from the transmitted density level. That is, a problem can arise that the region which should be identified as a photograph region is erroneously detected to be a character region due to the large density level change thereof. Such erroneous identification causes the deterioration in the frame quality of the photograph region of the output image transmitted from a printer or the like.
The image information correction is performed in a forward stage in which operation of distinguishing between a character region and a photograph region is conducted. Therefore, a further problem arises if, for example, an intense contrast is set for the image reading portion, as a photograph portion whose density difference has been enlarged can be erroneously identified as a character region.
Furthermore, related disclosure assignment by the assignee of the present invention, is disclosures in U.S. Pat. Nos. 4,414,581, 4,786,916, 4,709,274, 4,701,807, 4,723,173, and 4,686,579, and in the continuation application of U.S. Ser. No. 611,124 filed May 17, 1984, U.S. Ser. No. 22,513 (application date Mar. 9, 1987), U.S. Ser. No. 682,346 (application date Dec. 17, 1984), U.S. Ser. No. 812,308 (application date Dec. 23, 1985), U.S. Ser. No. 819,132 (application date: Jan. 15, 1986), and U.S. Ser. No. 925,247 (application date: Oct. 31, 1986). However, further improvement has been desired.